1. Apply an AD filter on the Source or Destination User fields in the global filter list (this is also supported in any location where source user is a filter option; reporting, correlation, views, etc):

2. If you want a view to be built around AD, you can use the Filter component (last one to the right) from the View Editing Toolbar options to start with AD and then build the view from there. As an example, this image started with AD and then shows all the events each user or AD group has logged.